1. Field of the Invention
The present invention is directed to a compensating thread brake (and in particular to providing braking to warping creels) comprising a mechanical thread tension comparison means and a setting member coupled therewith, which influences the braking force operating upon the threads.
2. Description of Related Art
In a known compensating thread brake of this type (DE PS 30 35 765), the thread which is to be subject to the braking force is led through five pins, of which two are stationary and three are attached to a comparison lever. This device operates under the influence of (a) the thread tension, which influences a thread deflecting position, and (b) a "desired value" spring operating in a direction opposed to the deflecting direction, as well as (c) an eddy current damping arrangement.
When the thread tension is too great, the comparison lever swings in such a direction that the deflection angle and thus the braking force of the five pins is reduced. If the thread tension is too small, the comparison lever swings in the opposite direction, whereby the braking force is increased. The disadvantage of this arrangement is that during the braking step, the threads are exposed to friction. This is damaging for many materials due to mechanical and thermal factors.
In another compensating thread brake known in the art (DE OS 27 11 823), the travelling thread at least partially surrounds a roller and thus rotates it. The inside of this roller is provided with, suitably, a controllable braking arrangement. An oil filling and the air displacement of a cooling jet is utilized as the braking working fluid. The regulation is a result of the change in the oil surface layer in a narrow space, which is formed between a stationary and a rotating part and may be altered in dependence upon the loading. As a result thereof, there are considerable temperature increases in the oil. Furthermore, the sealing of the oil filling is problematic. Furthermore, the braking force depends not upon the thread tension, but rather upon the thread speed.
Accordingly, an object of the present invention is to provide an improved, compensating thread brake, which keeps the thread tension substantially constant without subjecting the threads to impermissible mechanical or thermal stress due to friction.